Midterm ITCS 4120/5120 Fall 2006 – Results & Answers

Professor Zachary Wartell

Grades:

98
97.5
93
91
84.5
80
77
43

Approximate Letter Grade:

90-100 / A
75-90 / B
60-75 / C
< 60 / D

Midterm ITCS 4120/5120 Fall 2006

Score is out of 100 points. There are 10 questions. Note, different questions are worth different amount of points. Generally, the later questions are longer and worth more points.

Name: ______

1)  [3pts] List and define two precise measures of resolution of a display.Any two of the following:

dot pitch – distance, usually in mm, between, pixels on surface of a display

cycles per degree [display] – pixel count divided by FOV of display for given view position and display size divided by 2

cycles per degree [eye] – number of cycles of light and dark bands per degree that the human eye can distinguish (20/20 vision yield 30 cycles/degree in humans)

2)  [3pts] What are the general geometric properties preserved by an affine transformation?

-straight lines map to straight lines

-parallelism is preserved

-distance ratios are preserved

-points map to points vectors to vectors

3)  [3pts] Define aliasing (from a signal processing perspective).

High frequency signal components masquerading as low frequency signal components due to insufficient sampling rate

4)  [3pts] Define the term metamer.

A spectral power distribution of light for a light source is the power emitted by the source for each wavelength of light. A spectral power distribution, X, is a metamer to a second spectral power distribution, Y, if the power distributions differ but the human eye perceives the two light sources as the same color.

5)  [5pts] List and define the three different user interface input modes.

request mode [non GUI] – program statement requests input from user the program does not continue executing past that statement until input is received

sample mode [GUI] – program statement polls or samples input from user input device. If input data is available the input is returned from the function call. Otherwise, the function call return immediately and indicates no input data was available.

event mode [GUI] – program asks the GUI library to call an application program function when a particular input event is received

6)  [9pts] Illustrate the basic components of a CRT display. Describe the purpose of each component in a one sentence/phrase per component. (You should label at least 5 components)

ITCS 4120-Introduction (C).ppt, Slide #32

7)  [9pts] Illustrate the basic architecture of a computer graphics workstation at the level of key processors, buses, memory, etc.

ITCS 4120-Introduction (C).ppt, Slide #50

8)  [9pts] Illustrate and label in a much detail as possible the components and distinguished locations on the human eye (you should label/name at least 8 components).

ITCS 4120-Introduction (C).ppt, Slide #67

Labels – lens, cornea, pupil, retina, fovea, optical disk/blind spot, rods & cones,

9)  [28pts] Draw the global Edge Table for the polygon below. Next, draw the sequence values the Active Edge Table (AET) would be assigned during the rasterization of this polygon. Also show the y coordinate of the scan-line that the rasterization algorithm is working on, when the AET has each these different assigned values.


10) [28pts] Given the two coordinate systems A and B shown in the diagram: a) What is the matrix MB←A that transforms a point’s coordinate given in A into its coordinate in B? (From inspecting the diagram you should be able to give the exact real number values of the elements in the matrix—also its ok to leave results in a form like cos 45 if you want).b) If you had to compute MB←A by concatenating together only elementary matrices (translations and rotations, scales , and shears, etc about the origin) what would the sequence of these elementary matrices be? You should leave your answer as a sequence of matrices to be concatenated and for each matrix indicate what type of elementary matrix it is.